Petroleum wells can be naturally flowing, injecting or can be produced by any means of artificial lift. Referring to FIG. 1, a diagram of a typical sucker rod pump used in oil wells is described. Well (10) may include a well bore (11) and a pump assembly (12). Pump assembly (12) may be formed by a motor (13) that supplies power to a gear box (14). Gear box (14) is operable to reduce the angular velocity produced by motor (13) and to increase the torque relative to the input of motor (13). The input of motor (13) may be used to turn crank (15) and lift counter weight (16). As crank (15) is connected to walking beam (17) via pitman arm (18), walking beam (17) may pivot and submerge plunger (19) in well bore (11) using bridle (20) connected to walking beam (18) by horse head (21). Walking beam (17) may be supported by sampson post (22).
As shown in FIGS. 1-2, well bore (11) may include casing (23) and tubing (24) extending inside casing (23). Sucker rod (25) may extend through the interior of tubing (24) to plunger (19). At the bottom of well bore (11), in oil bearing region (26), casing (23) may include perforations (27) that allow hydrocarbons and other material to enter annulus (28) between casing (23) and tubing (24). Gas may be permitted to separate from the liquid products and travel up the annulus where it is captured. Liquid well products may collect around pump barrel (29), which contains standing valve (30), as shown in FIGS. 3A-3B. Plunger (19) may include traveling valve (31). During the down stroke of the plunger (FIG. 3B), traveling valve (31) may be opened and product in the pump barrel (29) may be forced into the interior of tubing (24). When the pump begins its upstroke (FIG. 3A), traveling valve (31) may be closed and the material in the tubing may be forced up the tubing by the motion of plunger (19). Also, during the upstroke, standing valve (30) may be opened and material may flow from the annulus in the oil bearing region and into the pump barrel.
As can be seen from FIG. 1, where the product flowing into the well bore contains entrained and free gas, that gas can enter the pump and reduce the volumetric efficiency of the pump. For instance, the hydrocarbon production stream can include both liquid and gaseous products that are a natural byproduct of the producing wells. As hydrocarbons and water flow through the formation, gases can travel in the flow stream either separate from the liquid products or dissolved within the liquid products. The gases are carried into the production tubing and can cause problems with artificial lifting mechanisms, such as rod pumps, by reducing the volumetric efficiency of the pump.
Gas interference occurs in situations when the pump is filling with a considerable amount of free gas that is not separated before entering the pump. If the amount of free gas entering the pump can be reduced, the volumetric efficiency of the pump can be improved, or the total pump capacity can be increased.